1. Field of the Invention
The present invention pertains to a power converter module in which optionally either a first input area designed to be connected to a first, predetermined electric potential or a second input area intended to be connected to a second predetermined electric potential can be electrically connected to an output area. The module includes at least one group of switches, where the minimum of one group of switches has two semiconductor switch units, each of which has a gate terminal. An input terminal of one of the semiconductor switch units is connected to the first input area and an input terminal of the other semiconductor switch unit is connected to the second input area, and each of the semiconductor switch units has an output terminal connected to the output area.
2. Description of the Related Art
These types of power converter modules are used, for example, in the devices called converters, which serve to excite multiphase electric motors such as those of the synchronous or asynchronous type. A schematic circuit diagram of a converter of this type for a three-phase electric motor is shown in FIG. 1. It can be seen that the converter 10 shown there has three converter modules 12, 14, 16. Each of the three motor phases 18, 20, 22 is excited by one of the converter modules 12, 14, 16. Because the three modules 12, 14, 16 are identical to each other in principle, the basic design of the modules will be described below with reference to the converter module 12.
The converter module 12 has, for example, four groups 24, 26, 28, 30 of semiconductor switch units 32, 34, these groups being connected in parallel to each other. Each of the semiconductor switch units shown in the example consists of an IGBT (insulated gate bipolar transistor), serving as a so-called power switch element. Each of these IGBTs has a gate G, serving as the gate terminal, and emitter and collector terminals, which are to be connected to each other. The collector terminal of the IGBT 32 is connected conductively to the emitter terminal of the IGBT 34. These two terminals C and E of the IGBTs 32 and 34 form the output terminals connected to the associated phase 18. The emitter terminal E of the IGBT 32 forms the input terminal of its transistor and is connected conductively to the input side 36, which is at the potential xe2x88x92V. In a corresponding manner, the collector terminal C of the IGBT 34 forms the input terminal of its transistor and is connected conductively to the input side 38, which is at the potential +V. Depending on whether the potential +V or xe2x88x92V is to be applied to the phase 18, one of the IGBTs 32 or 34 of the associated groups of switches 24, 26, 28, 30 will be switched to the conducting state, while the other remains nonconducting. In this way, it is possible to reverse the polarity of the various motor phases as required. Several IGBTs must be connected in parallel especially because, in the case of powerful electric motors, the currents flowing through the system during operation are very high, reaching as much as 400 A, for example. The individual power switch elements such as IGBTs or even MOSFETs, however, are usually suitable for currents of up to only 50 A. By connecting several of these power semiconductor switch elements in parallel, therefore, it is possible to adapt the power conversion in a stepwise manner to the requirements of the concrete application.
Adapting the individual modules of a converter of this type to the prevailing requirements usually calls for the development of special circuits. This process includes the production of the appropriate printed-circuit boards, the substrates of which are usually made of ceramic, and the insertion of the various power transistors, these circuits being designed with the goal of minimizing the inductances and maximizing the thermal tie-in to the existing cooling systems. It is very expensive to develop modules of this type, but even with the use of very expensive materials such as the ceramic substrates and expensive fabrication techniques for inserting the individual power transistors, the end result is still an assembly which is susceptible to damage from the loads which occur during actual operation. Especially the alternating thermal loads associated with the switching processes can lead to fractures, a susceptibility which is also promoted by the vibrations which occur when such units are used in motor vehicles, for example. As a result of the internal inductances which are present, the problem of so-called over-voltage transients also occurs frequently when current is switched from one transistor to another.
It is the object of the present invention to provide a power converter module which can be produced at favorable cost and which offers improved operating characteristics at the same time.
According to the invention, the two semiconductor switch units of the minimum of one group of switches are positioned facing each other in such a way that at least the output terminals thereof are opposite each other.
Because the arrangement according to the invention is designed so that the distance between two semiconductor switch units is as short as possible, especially with respect to the current pathway extending from the first to the second input area, it is ensured that the inductances of these groups of switches, which can be referred to as half-bridges, are low. Orienting the individual units of a group of switches so that they are facing each other, furthermore, also makes it possible to xe2x80x9cstackxe2x80x9d several of these groups easily on top of each other, with the result that it becomes comparatively simple to design the substrate during the development process, and at the same time the overall arrangement becomes highly compact.
It is possible, for example, for each of the semiconductor switch units of the power converter module according to the invention to have a switch housing, for the connecting sides of the switch housings to be arranged facing each other, at least the output terminals being provided on these connecting sides of the housings, and for the switch housings of the two semiconductor switch units to be offset with respect to each other in a housing offset direction in such a way that the two output terminals face each other essentially without any offset in the housing offset direction.
The use of switch housings for the individual semiconductor switch units has the result that the essential switching elements of the units are protected within the housing and thus more effectively shielded from external influences, especially mechanical influences.
In a preferred embodiment of the present invention, it is possible to provide the gate terminal, a first contact area of a first contact terminal, and a second contact terminal on the connecting side of the housing of each semiconductor switch unit and also to situate the second contact terminal of one of the semiconductor switch units, i.e., the terminal serving as the unit""s output terminal, opposite, and thus in electrical contact with, the first contact area of the first contact terminal of the other semiconductor switch unit, i.e., the area serving as at least part of its output terminal.
So that it is possible to make the most efficient possible use of the space which is available or required in the power converter module according to the invention, it is proposed that a second contact area of the first contact terminal be provided on the switch housing of the semiconductor switch unit, which second contact area is connected conductively to the first contact area; that the second contact area of the one semiconductor switch unit, i.e., the area serving as its input terminal, be connected conductively to the first input area; and that the second contact area of the other semiconductor switch unit, i.e., the area serving as part of its output terminal, be connected conductively to the output area.
In an alternative design of the power converter module according to the invention, it can also be provided that the first contact area of the one semiconductor switch unit, i.e., the area serving as its input terminal, is connected conductively to the first input area. Here, too, it is possible for a second contact area of the first contact terminal to be provided on the switch housing of the semiconductor unit, which second contact area is connected conductively to the first contact area, and for the second contact area of the other semiconductor switch unit, i.e., the area serving as part of its output terminal, to be connected conductively to the output area.
In a design of this type, it is also preferable for the second contact terminal of the other semiconductor switch unit, i.e., the terminal serving as its input terminal, to be connected to the second input area.
According to another aspect of the present invention, each of the semiconductor switch units has a switch housing, where the gate terminal, optionally a first contact area of a first contact terminal, and a second contact terminal are provided on the connecting side of the housing of each semiconductor switch unit, and the semiconductor switch units of the minimum of one group of switches are positioned so that the connecting side of the housing of one of the semiconductor switch units faces the rear of the housing (i.e., the side opposite the connecting side) of the other semiconductor switch unit. This arrangement also results in the closest possible packing of the individual semiconductor switch units, which is especially advantageous in cases where a large number of groups of switches is present in a single module.
So that the units can be packed as closely together as possible, it is also advantageous for the semiconductor switch units of the minimum of one group of switches to face each other essentially without any offset.
So that the necessary conductive pathways or traces on the substrate can also be kept as short as possible in this embodiment for the purpose of avoiding inductance problems as completely as possible, a second contact area of the first contact terminal can be provided on the switch housing of the semiconductor switch unit, which second contact area is connected conductively to the first contact area. The second contact terminal of one of the semiconductor switch units, i.e., the terminal serving as its output terminal, can be connected conductively to the second contact area of the first contact terminal of the other semiconductor switch unit, i.e., the area serving as its output terminal. It is possible, for example, for the second contact area to be provided on the bottom of each of the switch housings in question.
As already discussed above, it is necessary especially in the case of powerful electric machines to design the converter modules to carry comparatively high currents in the range of several 100 A. It is therefore proposed that a plurality of groups of switches be provided and that the semiconductor switch units of one of the groups of switches be arranged in a first row and that the semiconductor switch units of the other group of switches be arranged in a second row. The arrangement of these semiconductor switch units in rows on the substrate guarantees the closest possible packing and also makes it comparatively easy to lay out the conductive pathways to be provided on the substrate for the various input and output areas.
So that the individual input and output terminals can be brought easily into contact with the various potentials or phase connections, it is proposed that all the input terminals of one set of semiconductor switch units be connected or connectable to a conductor system of the first input area, that all the input terminals of the other set of semiconductor switch units be connected or connectable to a conductor system of the second input area, and that all the output terminals of the semiconductor switch units be connected or connectable to a conductor system of the output area.
It is possible here, for example, for the conductor system of the first input area and/or the conductor system of the second input area and/or the conductor system of the output area to comprise a conductor rail extending along the rows of semiconductor switch units. In another embodiment, contact with the various potentials can also be established alternatively or additionally by designing the conductor system of the first input area and the conductor system of the second input area in the form of conductor plates, which extend essentially parallel to each other and which are or can be situated above the rows of semiconductor switch units. This arrangement is especially preferred, because it also makes it possible to connect several adjacent modules to the various potentials with the same plates.
So that the inductances can also be minimized in these areas of contact with the potentials, it is proposed that at least certain parts of the conductor rails or conductor plates assigned to the first and second input areas rest against each other across a layer of insulating material.
In the power converter module according to the invention, furthermore, it is also possible for all of the gate terminals of one set of semiconductor switch units to be connected to a gate line of the first row of semiconductor switch units preferably by way of resistors, and for all of the gate terminals of the other set of semiconductor switch units also to be connected to a gate line of the second row of semiconductor switch units preferably by way of resistors.
So that heat can be carried away from the area of the individual power switches as efficiently as possible with the lowest-cost design, it is proposed that the minimum of one group of switches be mounted on an insulated metal substrate.
As already explained, each of the individual semiconductor switch units can comprise at least one IGBT semiconductor switch element (insulated gate bipolar transistor) or at least one MOSFET semiconductor switch element (metal oxide semiconductor field-effect transistor).
So that the above-mentioned mechanical loads exerted on these types of semiconductor switch elements can be minimized, it is proposed that the minimum of one semiconductor switch element be embedded in the switch housing.
The present invention also pertains to a power converter device for a multiphase electric machine, in which a power converter module according to the invention is assigned to each phase of the electric machine.
As already discussed, it is possible in this type of design of a converter device for all of the input terminals of the one set of semiconductor switch units to be connected or connectable to the conductor plate of the first input area and for all the input terminals of the other set of semiconductor switch units to be connected or connectable to the conductor plate of the second input area.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.